Substantial efforts have been made on behalf of the petroleum industry in order to analyze petroleum products at various stages of product production. For example, analysis attempts have been made on crude mineral oil being extracted from the ground or crude vegetable oils extracted from plant life as well as various components present within final motor oils and functional fluids. Such analyses were carried out in order to acquire specific information with respect to the components present witin the petroleum products. Such information allows the manufacturer to: (1) monitor the synthesis and determine the composition and structure of new additives present within petroleum products; (2) obtain additional information with respect to processing and blending control parameters; (3) detect and determine the additive content of lubricants of unknown formulation; and (4) accurately track additive depletion within motor oils and functional fluids during use. These four applications can relate, like the present invention, to uses connected with the analyses of finished products as opposed to an analyses of crude oil materials. The analyses of crude oil materials is distinct from the above in that such analyses is generally directed to obtaining information which will allow refiners to carry out more efficient oil refining techniques.
It is well known that a large number of synthetic chemicals is added to different types of lubricants in order to improve the properties of lubricants during their use within hostile environments such as the high temperature and pressure conditions within an internal combustion engine. Prior to the 1930s, a well-refined mineral oil was sufficient. However, engine demands have increased requiring the use of antioxidants in diesel engine lubricants to prevent oxidation of the base oil with consequent formation of corrosive acids and a rapid increase in viscosity. Subsequently, metal soaps were added as detergents to reduce engine deposits, particularly in the piston ring zone.
The auto industry introduced increasingly powerful internal combustion engines during the 1950s bringing about the development of highly sophisticated motor oils. The Lubrizol Corporation was and continues to be a leader with respect to the development of such sophisticated motor oils which in some instances contain up to 10% of a complex additive mixture conferring properties upon motor oils such as detergency, dispersancy, antioxidant properties, antiwear properties, rust inhibition, viscosity index improvement, pour point depressancy, etc. Different types of engines require different additives with high speed, high compression engines such as present day aviation gas-turbine engines making extreme demands on mineral oils. As the conditions to which the oil is subjected are made increasingly severe, the amount of additive included must be increased in order to provide the properties such as those referred to above. For example, with respect to aviation lubricants, such are now based on diesters or neopentylpolyol esters with hindered phenolic or amine antioxidants and antiwear additives such as aryl phosphates. Present day petroleum chemists consider such lubricant products to consist of 100% additive blends.
With the complexity and amount of additives present within lubricants increasing, it is clear that a determination of the additives present within lubricant oils continually presents analysts with challenging problems. In the past, the elemental analyses for metals such as calcium, barium, zinc and phosphorous might give the analysts useful information. However, at present, there is and has been a distinct trend towards low-ash or ashless dispersants within motor oils making the analyses for such metals of little use. Further, since such metals may be present within a variety of different lubricant additive compounds, and the structure of such compounds containing these metals may vary greatly, analyses for these metals yields little useful information.
In order to deal with such problems such as the increased number of additive compounds being included within lubricants and the increased complexity of the structure of such compounds, analysts have continued to develop sophisticated analytical techniques such as high-performance liquid chromatography (HPLC) and gel permeation chromatography (GPC). (See "Chromatography in Petroleum Analysis," Vol. 11, Knoaus H. Altgelt, Editor, Chevron Research Company, Richmond, Calif., 1979, chapter 17.)
Cox, R., "The Characterization and Quantitative Analysis of Dialkyl and Diaryl Dithiophosphates by Thin-Layer Chromatography and Densitometry," Journal of Chromatography, 105 (1975) pages 57-64. The article discloses methods of identifying dialkyl and diary dithiophosphates (DDPs) by thin-layer chromatography and subsequent quantitative analysis by thin-layer densitometry. The DDPs are reacted with an excess of iodine and the reaction product is chromatographed on silica gel.
Hill, M. et al, "Dialysis of Petroleum Products," presented before the Division of Petroleum Chemistry in American Chemical Society, New York, Sept. 11-16, 1960. The paper discloses some preliminary qualitative and quantitative studies on the application of dialysis for the separation of colloidal components from a variety of petroleum products.
Fialko, M. M. et al, "Kinetics of Dialysis of Motor Oil Additives," All-Union Scientific-Research Institute for Petroleum Processing (VNII NP), No. 9, pages 25-26, September, 1982. The paper discusses the effects of various factors on the process of separation by dialysis as applied to motor oil additives. Specifically, the paper relates to determining information with respect to the kinetics of dialysis on rubber membranes in hydrocarbon solvent medium.
Jenkins, G. I. et al, "The Analysis of Lubricants and Additive Concentrates Using Spectroscopy and Physical Methods of Separation," The Institute of Petroleum, Vol. 51, No. 93 (January 1965). The paper discloses the analysis of lubricants and additive concentrates using spectroscopic techniques in combination with physical methods of separation.
Coates, J. P., "The Analysis of Lubricating Oils and Oil Additives by Thin-Layer Chromatography," Journal of the Institute of Petroleum, Vol. 57, No. 556 (July 1971). The papers discusses the use of thin-layer silica gel chromatography in the routine analysis of lubricating oils and their additives.
Taulli, T. A., "Evaluation of Isomeric Sodium Alkenesulfonates via Methylation and Gas Chromatography," Journal of Chromatographic Science, No. 7 (November 1969). The paper discloses the conversion of non-volatile sodium salts of linear alkene sulfonates in the C.sub.16 range to volatile compounds which are then qualitatively evaluated by gas chromatography.
Separation methods such as the above referred to chromatography methods have met with some success with respect to the isolation of pure materials. Other isolation methods such as dialysis, classical adsorption chromatography silica and ion exchange resin, thin layer chromatography (TLC) as well as the analytical scale and the quantitative techniques of high performance liquid and gel permeation chromatography have been of use with respect to the routine determination of additives present in lubricants. Such separation techniques are utilized in combination with modern spectrascopic methods such as infrared, nuclear magnetic resonance, ultraviolet, mass spectroscopy and other modifications of these spectroscopic methods in order to identify groups and determine structures of additives present within such isolated components of modern lubricants.
The complexity of isolating and identifying additives within modern lubricants is vastly complicated by the fact that pure chemicals are rarely used as additives in modern lubricant compositions. As opposed to the use of pure chemicals, the additives are often in the form of mixtures of a vast number of different but closely related molecular structures which mixtures can provide improved performance characteristics over a wide range of operation conditions. The method of analysis of the present invention allows for the precise analysis of high molecular weight dispersants within motor oils with consideration to the increase complexity of such dispersants and other components present within motor oils.